This invention relates in general to apparatus for cutting sheet material and deals more particularly with a method for sharpening the cutting edges of a blade on a numerically controlled cutting apparatus of the type used in cutting pattern pieces from sheet material layups.
The use of numerically controlled cutting tools in the garment, automotive and other industries where fabric cutting is required is well established. Such numerically controlled equipment is capable of simultaneously cutting large numbers of pattern pieces from layups of material with high speed and accuracy. A cutting program controls operation of the cutting tool and causes it to translate through a layup which comprises high or deep layers of material while the layup is held in spread condition on a cutting table. Relative movement between the cutting blade and the layups can be produced by moving the cutting blade or the layup or both under program control, as it is well known in the art.
Apparatus of the aforedescribed general type has been developed which utilizes a vertically reciprocating blade sharpened along both its leading and lower edges. Such apparatus, which may be used to cut material with both slicing and chopping action, is particularly advantageous for use in cutting tough material, such as denim and upholstery fabrics, and allows cutting of relatively high piles of such difficult-to-cut materials. However, the cutting edges of the blade must be kept in sharpened condition to maintain the efficiency and speed of the cutting apparatus and to avoid occurrence of ragged edges on cut woven materials.
Heretofore, apparatus and methods have been available for sharpening only the leading edges of reciprocating cutting blades on apparatus of the aforedescribed general type. Typical blade sharpeners of this type and which utilized this method of sharpening are illustrated and described in my U.S. Pat. No. 4,033,214, issued July 5, 1977, and assigned to the assignee of the present application, and in U.S. Pat. No. 3,507,177, to Baldwin, issued Apr. 21, 1970, and assigned to Cincinnati Milling Machine Co., Cincinnati, Ohio. The apparatus and methods illustrated by the aforesaid patents are quite suitable for sharpening a blade which cuts with a slicing action and wherein a lower sharpened edge of the blade is used only occasionally, as in initially penetrating the material to be cut. However, a problem is encountered in sharpening the lower cutting or chopping edge and maintaining the latter edge of a blade in sharpened condition when the blade is used to cut with a chopping action. The present invention is concerned with this problem.